Generally, optical imaging systems having flat focal plane sensors include a photon sensor, a telescope, and an electronic read out system. Focal surfaces are generally curved (see FIG. 1A), while detector arrays are generally flat (see FIG. 1B). Existing systems use electronic focal plane sensors and attempt to work around aberration limitations by using compensators that attempt to flatten a given wave front (see FIG. 1A and FIG. 1B as described in S. B. Rim, et al., “The optical advantages of curved focal plan arrays”, Optics Express 16, (2008)). Furthermore, existing technologies use bending of thinned charge coupled device arrays (patented 2000 in Germany, DE10004891C2 by Astrium GmbH, EADS subdivision). Bending can easily lead to breakage of the optical device. Several academic groups use similar approaches, e.g. “A hemispherical electronic eye camera based on compressible silicon optoelectronics”, University of Illinois at Urbana-Champaign, Nature, 454, 748, 2008.
Additional patents describe techniques where silicon is mechanically bent into a desired shape: U.S. Pat. No. 6,849,843 B2, to Ansorge et al. describes the fabrication of a curved detector by bonding the sensing element to a flexible carrier substrate that can be bent to the desired curvature. US Patent Application Publication No. 2005/0109918 A1, to Nikzad et al. describes the use a deformable membrane as a curved detector. U.S. Pat. No. 6,985,184 B2, to Sato is motivated by the need for further miniaturization for cameras. According to Sato, a camera can be miniaturized by the use of a curved “pick-up surface”. This patent describes the general camera but not how the curved surface from the “pick-up” system is formed. This patent cites the above mentioned U.S. Pat. No. 6,849,843 B2 to Ansorge et al. U.S. Pat. No. 6,259,085, to Holland describes the fully depleted backside illuminated charge coupled device array; and US Patent Application Publication 2006/0180834 A1, to Holland describes how to improve a fully depleted backside illuminated charge coupled device array design by enabling higher voltages.
State-of-the-art cameras, such as cameras on UAVs or backup cameras on automobiles are examples, of the trade-off between field of view and weight. In addition they have insufficient spectral range and non-uniform illumination over the focal plane for a large field of view. This is due to their need for multiple lenses to correct for spherical and other optical aberrations due in part to relying on flat focal plane detectors. A simple curved focal plane (analogous to the human eye, where the retina acts as the curved focal plane) would allow for a very wide field-of-view without the aberrations encountered in a flat focal plane.
Therefore, the need exists for the development of optical detector devices which simplify adjoining optics in telescopes and which reduce occurrences of optical aberrations associated with large corrective optics used to conform to flat detectors.
Furthermore, the need exists for the development of curved CCD detectors, which match the contour of curved focal plane of an optical device such as a telescope.
Therefore, the need exists for a low cost fabrication method to produce a photon detector or focal plane array on a curved silicon surface without the need to mechanically bend a silicon substrate into a desired shape.